1. Field of the Invention
Embodiments of the present invention generally relate to an apparatus and methods for rinsing and drying semiconductor substrates.
2. Description of the Related Art
As semiconductor device geometries continue to decrease, the importance of ultra clean processing increases. Aqueous cleaning within a tank of fluid (or a bath) followed by a rinsing bath (e.g., within a separate tank, or by replacing the cleaning tank fluid) achieves desirable cleaning levels. After removal from the rinsing bath, absent use of a drying apparatus, the bath fluid evaporates from the substrate's surface causing streaking, spotting and/or leaving bath residue on the surface of the substrate. Such streaking, spotting and residue can cause subsequent device failure. Accordingly, much attention has been directed to improved methods for drying a substrate as it is removed from an aqueous bath.
Marangoni drying is generally used in cleaning, rinsing and drying semiconductor substrates. Marangoni drying generally creates a surface tension gradient to induce bath fluid to flow from the substrate in a manner that leaves most surface areas on the substrate virtually free of bath fluid, and thus may reduce streaking, spotting and residue marks. During Marangoni drying, a solvent miscible with the bath fluid (e.g., isopropyl alcohol (IPA) vapor) is introduced towards a fluid meniscus which is formed as the substrate is lifted from the bath or as the bath fluid is drained past the substrate. The solvent vapor is absorbed along the surface of the fluid, with the concentration of the absorbed vapor being higher at the tip of the meniscus. The higher concentration of absorbed vapor causes surface tension to be lower at the tip of the meniscus than in the bulk of the bath fluid, causing bath fluid to flow from the meniscus toward the bulk bath fluid.
During the cleaning and drying process, a substrate is generally supported by one or more end effectors. The end effectors are generally designed to contact the substrate near the edge with minimized contact point. Hydrophobic materials are employed in forming or coating the end effector to repel the bath fluid and reduce streaking and other defects. One problem with marangoni drying is that there are bath fluid droplets formed between the substrate and end effectors causing spotting defects in the substrates. Additionally, grooves or chips are easily formed on the current end effectors due to contact with substrates, thus requiring frequent replacement of the end effectors.
Therefore, there is a need for a substrate drying system having improved substrate contacting end effectors.